As a conjunction, one sense of as is “because”: As she was bored, Sue left the room.As also has an equally common use in the sense “while, when”: As the parade passed by, the crowd cheered and applauded. These two senses sometimes result in ambiguity: As the gates were closed, he walked away. (When? Because?) As … as is standard in both positive and negative constructions: The fleet was as widely scattered then as it had been at the start of the conflict. Foreign service is not as attractive as it once was.So … as is sometimes used in negative constructions (… not so attractive as it once was) and in questions (“What is so rare as a day in June?”). The phrase as far as generally introduces a clause: As far as money is concerned, the council has exhausted all its resources. In some informal speech and writing, as far as is treated as a preposition and followed only by an object: As far as money, the council has exhausted all its resources.As to as a compound preposition has long been standard though occasionally criticized as a vague substitute for about, of, on, or concerning: We were undecided as to our destination.As to sometimes occurs at the beginning of a sentence, where it introduces an element that would otherwise have less emphasis: As to his salary, that too will be reviewed.As to what and as to whether are sometimes considered redundant but have long been standard: an argument as to what department was responsible. See also all, because, farther, like1, so1.

though

[th oh] /ðoʊ/

conjunction

1.

(used in introducing a subordinate clause, which is often marked by ellipsis) notwithstanding that; in spite of the fact that; although:

Among some conservatives there is a traditional objection to the use of though in place of although as a conjunction. However, the latter (earlier all though) was originally an emphatic form of the former, and there is nothing in contemporary English usage to justify such a distinction.

though

c.1200, from Old English þeah, and in part from Old Norse þo "though," both from Proto-Germanic *thaukh (cf. Gothic þauh, Old Frisian thach, Middle Dutch, Dutch doch, Old High German doh, German doch), from PIE demonstrative pronoun *to- (see that). The evolution of the terminal sound did not follow laugh, tough, etc., though a tendency to end the word in "f" existed c.1300-1750 and persists in dialects.

as

adv.

c.1200, worn-down form of Old English alswa "quite so" (see also), fully established by c.1400. Equivalent to so; any distinction in use is purely idiomatic. Related to German als "as, than," from Middle High German also. Phrase as well "just as much" is recorded from late 15c.; the phrase also can imply "as well as not," "as well as anything else." Interjection of incredulity as if! (i.e. "as if that really could happen") is attested from 1995, an exact duplication of Latin quasi.